(1) Field of the Invention
This invention generally relates to the field of reconstructive vascular surgery and, more particularly, to a device and method for vascular anastomosis.
(2) Description of the Related Art
Since the first successful vascular anastomosis was performed at the turn of the century, the search for an easier and faster technique than conventional needle-and-thread suturing has challenged surgeons. Payer was the first to describe a technique for sutureless vascular anastomosis using a magnesium ring. (Metalles in den Chirurgie. Arch. Kiln. Chir. 62:67, 1900). This principle was modified by Nakayama et al. and further modified by Ostrup and Berggren into an apparatus for microvascular anastomosis which is commonly used today. (Nakayama et al., Surgery 52:918-931, 1962; First Scandinavian Seminar on Reconstructive Microsurgery, Gothenburg, Sweeden, October 1979, pp. 521-525, 1986. Although this apparatus has a number of advantages, it is still far from the ideal vascular anastomosis device. The wall of the arteries is usually too thick and rigid to permit the necessary vessel eversion. This problem is even more severe in diseased vessels and limits the use of this device in vascular surgery. Furthermore, the device is quite cumbersome and the surgical methods required for its use are difficult to master. Nonetheless, for lack of anything better, and because it saves operating time, the device is routinely used today in microvascular free flap surgery to anastomose veins.
An alternative to suturing the vessel, is the use of tiny staples or microvascular clips to bring vessel edges together circumferentially. (For example see Kirsch et al, The American Surgeon 12:722-727, 1992, which is incorporated herein by reference). Use of these staples is, however, limited by the problem that in order to achieve accurate placement of the staples, eversion of the edges of the vessel wall, and the avoidance of a "backwall" bite, an assistant is required to hold the vessel edges up while the staples are inserted. Not only is this inconvenient, such assistance is not always possible such as, for example, in endoscopic procedures.
The use of stents in vascular reconstruction can both facilitate the procedure itself and improve the outcome, particularly in small vessels and in veins. Temporary stents have been used in vascular surgery that are removed prior to complete closure of the anastomosis. These have been reported to improve the ease and rapidity of the anastomosis as well as decrease the danger of injury to the lumen and posterior wall and improve the percent of anastomoses remaining patent. (Wei et al., British J Plastic Surg 35:92-95, 1982, which is incorporated herein by reference). Soluble intravascular stents that dissolve and need not be removed have also been reported. Kamiji et al. used a polyethylene glycol stent that reportedly is washed away by the blood flow and dissolved after restoring blood flow. (British J Plastic Surg 42:54-58, 1989, which is incorporated herein by reference). In addition, stents have been reported that, upon completion of the anastomosis, can be melted or dissolved by warm isotonic saline and subsequently washed away in the blood on restoring blood flow (Cong et al, Microsurgery 12:67-71, 1991; Moskovitz et al, Annals Plastic Surgery 32:612-618, 1994, which are incorporated herein by reference). These groups used stents composed of a mixture of mono-, di-, and triglycerides that melt at temperatures near body temperature. Because the glycerides are normal elements in the blood stream, the stent was considered biocompatible.
Particular advantages reported on use of the stent with suturing of the anastomosis were an improvement in the accuracy and speed of the procedure, the minimizing of minor trauma, the avoidance of suture errors such as a partial bite of the opposite wall, the achieving of a better coaptation of cut edges, the avoidance of narrowing at the anastomosis sites, the achieving of even distribution between stitches, and the preventing of vasospasm (Cong et al., 1991). Use of the stent with fibrin glue was reported to have the disadvantage of producing aneurysms. Although one group used the stent in combination with sutures, neither used the stents in combination with staples. Use of staples would be expected to reduce the likelihood of aneurysm formation compared to the use of fibrin glue because of the staples firmly holding the media in close enough apposition to allow proper healing over time. Furthermore, staples would be expected to decrease the time required for the procedure compared to use of suturing with the stent.
The use of a stent in combination with staples has not been appreciated as an advantage over the staples alone in open field microvascular anastomosis inasmuch as it has been reported that a stent is not necessary with microclip anastomosis (Kirsch et al, 1992). In the non-vascular anastomosis of vasovasostomy, an absorbable stent was used in combination with microvascular clips. (Gaskill et al, Urology 40:191-194, 1992, which is incorporated herein by reference). The stent was hollow and composed of polyglycolic acid. Furthermore, the stent was not immediately absorbable as would be required for such a temporary stent in a vascular anastomosis. This group reported that the combination of an absorbable stent with microclips allowed a shorter time for completion of the procedure (7.6 v. 8.5 minutes) and required less care. Nevertheless, it was indicated that there was no advantage to using the stent because of a high percentage of granulomas following its use apparently resulting from the need for more clips to seal the anastomosis or from obstruction of the stent. The requirement for more clips may indicate a failure of the stent to fit snugly into the vessel. Furthermore, obstruction from the stent is likely to have been a result of the stent dissolving over a relatively long period of time. Moreover, this reference did not apply the technique using the slowly absorbable stent along with stapling to vascular anastomosis.
Thus, in performing a vascular anastomosis, it would be desirable to have an improved method that is easy and rapid and that does not require an expert surgical assistant and that also produces an eversion of the vessel edges and avoids a "backwall" bite.
One of the problems that can be associated with vascular anastomosis is the formation of thrombus at the anastomosis. The thrombus results from a gradual accumulation of platelets at the anastomosis and the formation of fibrin. The thrombus thus formed could eventually occlude the vessel. It would be desirable, therefore, to provide some means to diminish the likelihood of formation of a thrombus at the anastomosis site.